LED Measurements

LED Measurements

LEDs are increasingly replacing traditional light sources in a wide range of applications. They are small, cheap, power efficient, have longer lifetimes…and the list of advantages goes on.
As the laser’s use as a scientific research tool becomes more commonplace, so does the need to include accurate, objective measurements of the laser’s behavior.
They are becoming the light source of choice in industrial applications such as:

  • UV curing
  • Food and water anti-bacterial treatment
  • Medical applications of low power UV/VIS radiation
  • Illumination systems for medical use and machine vision, or for microscopy applications

As illumination light sources, LEDs were traditionally used in low-power applications such as instrument panel illumination or LCD screen backlighting; now, though, indoor and outdoor LED luminaires are becoming standard, as is the use of LEDs in the automotive industry.
In any industrial process, the ever-growing demands for efficient productivity require that the process be stable and predictable. In an LED-based process such as UV curing of adhesives for example, the LED source needs to be monitored so that peak performance can be maintained. Proper monitoring of correctly defined LED parameters can be used to raise a flag for triggering preventive maintenance, and can also enable process control, so that a drifting parameter can be automatically corrected and the process kept within its specified envelope – ideally without interruption.
Depending on the application, critical LED parameters might include irradiance on a surface (W/cm2), dosage (total J/cm2 deposited on a surface over time), or perhaps total emitted flux or power (in W). Sometimes spectral data is also important.
Measuring these parameters of an LED is a bit tricky, though; LEDs are not quite like lasers but are also not quite like lamps. Their beams are normally widely diverging, and their spectral distribution is typically a widened peak – not a narrow peak as in a laser, but not a broadband spread either.
For measuring irradiance and dosage, Ophir offers the PD300RM family of sensors. These are based on UV-enhanced photodiode detectors, calibrated over their entire specified spectral range; this means that one sensor can be used for a whole range of spectral peaks They also have integrated diffusers, giving the PD300RM sensors a cosine-corrected angular response so that effects of incidence angle are eliminated.
For measuring total emitted power, Ophir offers Integrating Spheres of various sizes and in various configurations. These are available with integrated sensors and fully calibrated, as well as without sensors for customers to use with their own sensors or perhaps – illuminated from the inside - as uniform wide-area light sources. Most Integrating Sphere models include several ports, to enable sampling of the light for additional measurement purposes such as spectral analysis.
Ophir also offers a photometric sensor, PD300-CIE, for measuring illuminance in units of Lux or Foot Candles.
Check out our online LED Sensor Finder to help you find the right sensor for your LED measurement.


Designing Low Cost Inspection Process for LED’s

In this application, our customer manufactures encoders that incorporate LED’s (light emitting diodes) that have a collimating lens attached. The LED’s produce between 850nm and 880nm at 2mW to 15mW, the beam sizes range from ¼” to ½”. Until now, a laser power meter has been used to verify the output wattage. Shining the beam on graph paper has been used to verify the beam size visually. Read more >

White Paper: Measuring LED Power with Thermal Sensors

LED’s are used today in many applications with the most prominent being the lighting of our homes, streets and businesses. Despite their clear advantages, measurement techniques of the power, flux and spectrum of LEDs is not very different from that of traditional types of lamps. Read more >

Relevant products